1. Field of the Invention
The present invention relates to a hydraulic apparatus for adjusting the timing of opening and closing of an engine valve, for changing the timing of opening and closing of intake valve and/or exhaust valve of an engine, according to the operation state of the engine, using an actuator which controls the flow of a working oil which flows therein. More particularly, the present invention relates to a hydraulic apparatus for adjusting the timing of opening and closing of an engine valve by which the cleaning of the actuator is possible.
2. Description of the Prior Art
Such hydraulic apparatuses for adjusting the timing of opening and closing of an engine valve are disclosed, as prior art, in JP7-139319A, JP7-139320A, JP8-28219A, JP8-121122A, JP9-60507A, JP9-60508A in which cam shafts are driven using a timing pulley synchronized with the engine crank shaft and a chain sprocket. A vane type valve timing mechanism is arranged between the timing pulley and the cam shaft, which is driven by an actuator using a working oil provided from an oil pump through an oil control valve (hereinafter to be called "OCV"), so as to rotate the cam shaft relative to the crank shaft, to advance or to retract the cam shaft relative to the crank shaft rotation. Thus the timing of opening or closing of engine valve relative to the engine shaft rotation is shifted, for the purpose of reducing exhaust gases and improving of fuel efficiency.
The actuator employed in such a hydraulic apparatus for adjusting the timing of opening and closing of an engine valve in the prior art has a structure that allows the rotor to slide in its housing, and a working oil is provided from an OCV, so as to rotate towards the timing advance direction or to the timing retard direction.
An actuator employed in such a hydraulic apparatus for adjusting the timing of opening and closing of an engine valve in the prior art has drawbacks caused by such a structure: sludge in the working oil provided into the actuator housing tends to deposit on the inner surface of the housing, because of the centrifugal force of the rotor; additionally, the rotor in a normal operation rotates rarely to the most advanced angle position, thus the sludge deposited on the inner surface of the housing tends to accumulate at the most advanced angle region (a portion of the housing inner surface to where the rotor does not reach), by being pushed by the rotor; this accumulation causes problems, when the rotor is shifted in a wide range, in such a case, the rotor is forced to climb over the accumulation of the sludge, this can be an obstacle to the function of the rotor.